Hashtags are strongly used in contexts of social mobilization to articulate related political positioning, forming symbolic links that demarcate the collective processes of signification. Yang (2016) argues that there is neglect in the study of digital activism in relation to its narrative form. And one of the ways to think this structure would be through the social use of multiplatform hashtags. They form hyperlinks through which it becomes possible to aggregate varied publications, in distinct media contexts and in varied temporalities, from a common significant form. Its growth depends on the expansion of social use and its mediating function is strengthened in the daily interactions, which connect the online and offline environments. They act, therefore, as mediating instances that mediate transmedia dynamics in social network connections. For Srivastava (2009), the transmedia dynamic offers important possibilities for the movements involved in social change. According to the author, there are decentralized actors who create entry points for issues and solutions related to the topic in multiple platforms and languages. This favors the creation of strategies to generate social impact, influencing the perception and construction of communities. For this reason, it is possible to note the emergence of transmedia activism, which happens through the process of generating awareness, engagement, action and structuring of change. This type of activism would be perceptible in narrative that runs through and encompasses the central theme, even if in a fragmented and varied way. This transmedia dynamic is permeated by varied mediation processes, usually from the combination of institutional actions and the productive activity of the audience on social networks connections. Its focus is to combine audiences and change agents with a particular worldview or specific action through local stories. Its main point is the use of local voice, aiming at community-centered participation. Through digital projection, these narratives gain visibility and can be expanded to a global level. Thus, they use multiple platforms to realize a cultural appropriation with the intention of crossing borders to promote the transformation. Based on the theoretical-methodological perspective of Peirce's semiosis (BERGMAN, 2010), this paper aims to investigate the mediating action of the hashtag #VemPraRua in the context of recent Brazilian protests between 2013 and 2018. For this investigation on social networks, automated collection procedures were used in order to reproduce possible trajectories of the hashtag under study. The Hashtagify.Me digital monitoring tool made it possible to view the network of hashtags generated around #VemPraRua over time, on Twitter and Instagram. Data analysis was based on the signic relations that conform Peircean semiosis, or mediation. The results pointed to a form of transmedia activism that operates by successive resignifications. Often, the hashtag has been used by groups with different interests and positions, which demonstrates the variety of mediation processes that permeate #VemPraRua's semiosis. References BERGMAN, MATS. C.S. Peirce on interpretation and colateral experience. Signs. Vol. 4: pp. 134-161, 2010. SRIVASTAVA, L. Transmedia Activism: Telling Your Story Across Media Platforms to Create Effective Social Change, 2009. Disponível em: <http://www.mediarights.org/news/Transmedia_Activism_Telling_Your_Story_Across_Media_Platforms_to_Create_Eff>. Acesso em: 30/07/2017. YANG, G. Narrative Agency in Hashtag Activism: The Case of #BlackLivesMatter. Media and Communication, 4 (4), 13-17, 2016. Disponível em: doi 10.17645/mac.v4i4.692. Acesso em: 21/08/2017.